Email Services

CounterMail

Kolab Now

Mailbox.org

MailFence

Namecheap (They host business emails.)

Posteo

Proton (One Proton account gives access to ProtonMail, ProtonVPN, Proton Calendar, and ProtonDrive.)

ProtonMail Bridge (“An application available to all paid users that enables the integration of your ProtonMail account with popular email clients, such as Microsoft Outlook, Mozilla Thunderbird, or Apple Mail.”)

Reagan.com 

Runbox

SimpleLogin (receive and send emails anonymously)

Skiff (“private, end-to-end encrypted workspace”; now also offers end-to-end encryption Email)

Soverin

Startmail (same company that built the Startpage search engine)

Thexyz

Thunderbird

Tutanota

Vivaldi (web browser that includes email)

Zoho (They also have a Notepad alternative.)